Baculovirus system for the expression of a gene therapy vector

ABSTRACT

The invention concerns a recombinant baculovirus genome useful for the expression of gene therapy vectors by means of a single infection.

Recombinant adeno-associated viruses (or rAAVs) are currently consideredto be the most promising viral vectors in gene therapy. However, theirlarge-scale production remains a limiting factor for the development oftherapies of this type. Production systems which exploit the capacity ofbaculoviruses to infect insect cells have thus been developed with aview to overcoming this problem, and for biosafety reasons (Urabe et al.2002; Hum. Gene Ther. 13: 1935-1943; US 20030148506; US 20040197895).According to the protocol initially proposed, infection of insect cellswith 3 different baculoviruses was required in order to provide the repand cap helper genes and the construct comprising the recombinant AAVvector containing the transgene required to form the recombinant viralparticle. A simplification of this system consists of the integration ofthe rep and cap genes into a single baculovirus resulting in aproduction system using 2 baculoviruses (rep/cap bac and transgene-bac)(Smith et al. 2009; Mol. Ther. 17: 1888-1896). Moreover, the group ofSergei Zolotukhin (Aslanidi et al. 2009; Proc. Natl. Acad. Sci. USA 206:5059-5064 and WO 2010/114948) has recently developed Sf9 cell linesstably transformed with the rep and cap genes. With such a cell line,infection with a single baculovirus (comprising in its genome thetherapeutic gene of interest flanked by ITR of an AAV) would make itpossible to obtain a recombinant AAV. However, this system has severaldrawbacks. Firstly, the generation of cell clones is fastidious and theclones obtained are often characterized by genetic instability whichresults in an exploitation window which is limited in time. In addition,a high frequency of packaging of foreign DNA which does not correspondto the vector of interest (sequences of rep and cap and of genes forresistance to an antibiotic) has been observed, thereby posing aconsiderable problem in terms of biosafety. Such clones are thusunsuitable for the production of batches of vectors intended forclinical use.

All the baculoviruses used in the studies mentioned above comprise theinsertion of the gene of interest (whether it is the rep and/or capgenes or the therapeutic gene of interest) into the polyhedrin cloningsite of the baculovirus genome. This site is conventionally chosen owingto the high levels of expression which can be obtained from this locus.This site is also used in the system developed by Luckow et al. (1993;J. Virol. 67:4566-4579) into which a bacterial origin of replication, akanamycin resistance gene and a “Tn7” recombination cloning site areinserted. This system is known as a bacmid. However, the use of thissole locus constitutes a limiting factor, in particular if it is desiredto be able to express several heterologous sequences from a singlebaculovirus. It is in this context that Noad et al. (2009) compared theconventional locus—polyhedrin (Tn7 of the bacmid, present at thepolyhedrin site)—with various potential cloning sites and identified 7additional loci (ctx, egt, 39k, orf51, pg37, iap2, odv-e56) in thegenome of AcMNPV allowing strong expression of heterologous genes (Noadet al. 2009; BMC Molecular Biology 10: 87; WO 2010/055292). It was alsoshown that various genes cloned in several of these loci can beexpressed concomitantly from the same genome. However, Noad et al. didnot show whether these alternative loci were effective for theproduction of recombinant AAV or any other recombinant viral vector,which was not obvious given the complexity of these viral vectors andthe major difficulties conventionally encountered during the productionthereof.

SUMMARY OF THE INVENTION

Surprisingly, it has been possible to show that recombinant AAVs can beproduced by virtue of a single baculovirus.

The invention thus relates to a recombinant baculovirus genomecomprising heterologous sequences encoding all the components requiredfor the production of a heterologous viral vector (i.e. the proteincomponents of the vector and its genome) inserted into loci selectedfrom the group consisting of the nonessential genes of the baculoviruswhich can be replaced with a sequence of interest without modifying thefunctioning of the baculovirus.

The invention in particular relates to a recombinant baculovirus genomecomprising one or more expression cassettes for the protein componentsrequired for the production of a heterologous viral vector, and arecombinant genome of a heterologous viral vector (also subsequentlyreferred to as heterologous genome), said expression cassettes and saidheterologous genome being inserted into one or more locus selected fromthe group consisting of the egt, polyhedrin, ctx, 39k, orf51, gp37, iap2and odv-e56, p10 and p94 loci. The baculovirus genome can in particularcomprise at least one expression cassette for the AAV rep and/or capgenes, inserted into said one or more locus. According to one variant,said rep and cap genes are contained in a single expression cassette, inparticular in reverse orientation, said cassette being more particularlyinserted into the egt locus. In one particular embodiment, therecombinant genome of a heterologous viral vector is an AAV recombinantgenome inserted into a different locus of the locus or loci used for theAAV rep and cap genes, said heterologous genome being in particularinserted at the level of the polyhedrin locus.

The invention relates, moreover, to a recombinant baculovirus genomecomprising one or more expression cassettes for the AAV rep and/or capgenes, said one or more expression cassettes being inserted into a locusselected from the group consisting of the egt, ctx, 39k, orf51, gp37,iap2, odv-e56, p10 and p94 loci of the baculovirus genome. Thisrecombinant baculovirus genome also preferably contains an AAVrecombinant genome in a locus selected from the polyhedrin, egt, ctx,39k, orf51, gp37, iap2, odv-e56, p10 and p94 loci of the baculovirusgenome, said AAV recombinant genome being inserted into a locusdifferent than the locus or loci used for the AAV rep and cap genes.

The recombinant baculovirus genomes according to the invention can inparticular be derived from the AcMNPV baculovirus. Moreover, therecombinant baculovirus genome of the invention can also have thecharacteristic of being deficient for the chitinase, cathepsin and p10genes.

When the recombinant baculovirus genome according to the inventioncontains a heterologous recombinant virus genome, said heterologousgenome may comprise a heterologous gene encoding a protein, aninterfering RNA or an antisense RNA, which is in particular therapeutic(so as to allow the production of a viral gene therapy vector).

According to one particular embodiment, the recombinant baculovirusgenome is a recombinant bacmid.

The invention also relates to a recombinant baculovirus, the genome ofwhich is a recombinant baculovirus genome, in particular a bacmid,according to the invention.

Moreover, the invention relates to a method for producing a recombinantbaculovirus, comprising culturing a prokaryotic cell containing therecombinant bacmid defined in the present application under conditionssuitable for the production of a baculovirus.

The invention also provides a eukaryotic or prokaryotic cell containingthe recombinant baculovirus genome disclosed, or infected with therecombinant baculovirus of the invention. Said cell may in particular bea mammalian cell (for example an HEK293 cell) or an insect cell derivedfrom the Spodoptera frugiperda or Trichoplusia ni lines (for example,the Sf21, Sf9, TN 5B1-4 or High Five cells).

The invention also relates to a method for producing viral vectors, inparticular viral gene therapy vectors. It is directed more particularlytoward a method for producing a recombinant AAV, comprising culturingthe recombinant baculovirus comprising the sequences required for theproduction of the protein or genetic components of an AAV, with a cell,in particular an insect cell (for example, an Sf9, Sf21, TN 5B1-4 orHigh Five cell), capable of being infected with said baculovirus, underconditions which allow the infection of the cell with the baculovirusand the production of said recombinant AAV.

FIGURE LEGENDS

FIG. 1. Monobac System for the production of rAAV vectors

The AcMNPV bacmid was inactivated for the chitinase, cathepsin and p10genes. The expression cassette for the AAV rep2 and cap8 genes wasinserted into the genome of the bacmid at the ecdysteroidUDP-glucosyltransferase (egt) locus, thus leaving the tn7 transpositionsite of the bacmid free for the insertion of the rAAV genome. A singlebaculovirus thus makes it possible to produce rAAV particles in insectcells.

FIG. 2. Study of the locus effect for expression of the AAV rep2 andcap8 genes

The expression of the AAV Rep and Cap8 proteins was monitored by Westernblot using baculoviruses expressing these proteins from the expressioncassette inserted at the Tn7 site of the bacmid or at the egt locus, 3days after infection of Sf9 cells. The protein expressionstandardization is monitored by measuring the expression of the P35baculovirus protein.

Monobac C1 & C2: AcbacΔCCΔp10-rep2cap8(EGT).

ΔCCP-SR660 C1 & C2: AcbacΔCCΔp10-rep2cap8(Tn7).

WT-SR660 C1: AcbacWT.

T+ AAV8 bulk: positive control for AAV8-mSeAP production.

ΔCCΔp10: bacmid from which the cathepsin, chitinase and p10 genes havebeen deleted.

Acbac: bacmid derived from AcMNPV.

FIG. 3. Study of the locus effect for expression of the AAV rep2 andcap8 genes

The expression of the AAV Rep and Cap8 proteins was monitored by Westernblot using baculoviruses expressing these proteins from the expressioncassette inserted at the Tn7 site of the bacmid or at the egt locus, 3days after infection of SD cells. The protein expression standardizationwas monitored by measuring the expression of the P35 baculovirusprotein.

Monobac C1 and C2: AcbacΔCCΔp10-rep2cap8(EGT).

Monobac Seap C1 & C2: AcbacΔCCΔp10-rep2cap8(EGT)-mSeAPTn7).

T+ AAV8 bulk: positive control for AAV8-mSeAP production.

FIG. 4. rAAV productivity

The rAAV productivity in the monobac system was evaluated. The resultsare given as rAAV titer (vg/ml—vector genome/ml). 4 replicates were usedper experiment, the error bar represents the standard deviation.

FIG. 5. rAAV productivity after purification by immunoaffinity

The rAAV productivity in the monobac system was evaluated afterpurification. The results are given as rAAV titer (vg/ml—vectorgenome/ml).

FIG. 6. Protein profile of the purified rAAV vectors

The protein profile of the rAAV vectors was evaluated after purificationby immunoaffinity. 5×10¹⁰ vg of rAAV were analyzed by SDS-PAGE andstaining of the gel with Coomassie blue.

(1) AAV8-mSeAP produced with the wild-type baculoviruses. 1^(st)baculovirus bacWT-rep2/cap8 (Tn7), 2^(nd) baculovirus bacWT-mSeAP. (2)AAV8-mSeAP produced with the baculoviruses deleted for the chitinase,cathepsin and p10 genes. 1^(st) baculovirus bacΔCCΔp10-rep2/cap8 (Tn7),2^(nd) baculovirus bacΔCCΔp10-mSeAP. (3) AAV8-mSeAP produced with thebaculoviruses deleted for the chitinase, cathepsin and p10 genes. 1^(st)baculovirus bacΔCCΔp10-rep2/cap8 (EGT), 2^(nd) baculovirusbacΔCCΔp10-mSeAP. (4) AAV8-mSeAP produced with the baculovirus deletedfor the chitinase, cathepsin and p10 genes. A single baculovirus used,bacΔCCΔp10-rep2/cap8 (EGT)-mSeAP (Tn7).

DETAILED DESCRIPTION OF THE INVENTION

The production of a viral vector, in particular a viral gene therapyvector, requires the expression, in the same cell, of the numerouscomponents of the viral vector. For example, in the case of theproduction a recombinant AAV in an insect cell, it is necessary toproduce, in the cell:

-   -   an AAV recombinant genome comprising a 5′ ITR (for Inverted        Terminal Repeat), and an expression cassette for a heterologous        nucleotide sequence of interest (at least one heterologous        nucleotide sequence of interest under the control of a promoter        which is effective for the expression of said gene in a target        cell defined below), and a 3′ ITR; and    -   the products of the AAV rep and cap genes.

A baculovirus expression system has been developed in order tofacilitate the production of viral vectors, in the sense that a singlebaculovirus is used to infect the host cells producing the viral vector.

The invention relates in particular to a recombinant baculovirus genomecomprising one or more expression cassettes for the protein componentsrequired for the production of a heterologous viral vector, and arecombinant genome of a heterologous viral vector (or heterologousgenome), said expression cassettes and said heterologous genome beinginserted into one or more loci selected from the group consisting of thenonessential genes of the baculovirus which can be replaced with asequence of interest without modifying the functioning of thebaculovirus.

In the context of the present invention, the “nonessential genes of thebaculovirus” are defined as genes which can be inactivated or removedfrom the genome of the baculovirus, without modifying its capacity togrow in insect cell cultures. These genes are genes which are involvedspecifically in ODV (Occlusion Derived Virus) production or genes whichare required for the manipulation of the host insect in the environment,but are not required on the scale of insect cells in culture (Cohen etal. 2009; Virologica Sinica 24: 359-414). According to one particularembodiment, the locus or loci is (are) selected from the groupconsisting of the polyhedrin, ctx, egt, 39k, orf51, gp37, iap2, p94, p10and odv-e56 loci, said locus being more particularly the egt locus.

In the context of the invention, the term “heterologous viral vector” isintended to mean a viral vector which is not a baculovirus. Theheterologous viral vector may in particular be an adenovirus, anadeno-associated virus, a retrovirus, in particular a lentivirus or aspumavirus, etc. More specifically, the recombinant baculovirus genomeaccording to the invention is capable of being used for the productionof viral vectors of any type intended to be used for introducing aheterologous nucleotide sequence into a cell, a tissue or an organism,in particular a viral vector for therapeutic purposes in humans oranimals (gene therapy vector).

In the context of the present invention, the term “expression cassette”is intended to mean a combination of elements required for theexpression of one or more genes. An expression cassette thus contains apromoter suitable for expression in a host cell, in particular aeukaryotic cell, more particularly an insect cell, and a polyadenylationsequence. Those skilled in the art have several cassettes for expressionin eukaryotic cells (in particular insect or mammalian cells) at theirdisposal.

As mentioned above, the recombinant baculovirus genome according to theinvention can be intended for the production of viral vectors of anytype, in particular viral gene therapy vectors. For example, therecombinant baculovirus genome can comprise one or more expressioncassettes for viral proteins required for the production of anadeno-associated virus, of an adenovirus, of a retrovirus, in particulara lentivirus or a spumavirus, etc. The genes required for the productionof such viral particles are well known to those skilled in the art, whowill adapt the present recombinant baculovirus genome to the particularviral vector that they wish to produce (Bagnis, Merten, Mezzina (guesteditors) 2005: Advanced methods for industrial production, purification,and characterization of gene vectors. Gene Ther 12(S1): 1-177).

According to one preferred embodiment, the recombinant baculovirusgenome according to the invention also comprises a viral gene therapyvector recombinant genome, said viral gene therapy vector recombinantgenome being inserted into a locus of the baculovirus genome asdescribed above. The viral gene therapy vector recombinant genomeinserted into the baculovirus genome will of course depend on the viralgene therapy vector to be ultimately produced. Thus, for the productionof an AAV, the viral gene therapy vector recombinant genome will be anAAV recombinant genome comprising a 5′ ITR, at least one heterologousnucleotide sequence of interest under the control of a promoter which iseffective in the target cell of the recombinant AAV produced, and a 3′ITR. For the production of a lentivirus, the viral gene therapy vectorrecombinant genome will be a lentivirus recombinant genome comprising a5′ LTR, a major splice donor site, a packaging signal covering the 5′part of the Gag gene, the Rev response element (RRE), the envelopesplice acceptor, at least one heterologous nucleotide sequence ofinterest under the control of a promoter which is effective in thetarget cell of the recombinant lentivirus produced, and a 3′ LTR, inparticular a 3′ LTR modified with a view to generating SIN(Self-INactivating lentivirus) vectors.

Thus, according to a first variant of the invention, the recombinantbaculovirus genome described is a baculovirus genome for the productionof an AAV vector.

In this respect, the invention also relates to a recombinant baculovirusgenome comprising one or more expression cassettes for the AAV repand/or cap genes, said one or more expression cassets being insertedinto a locus selected from the group consisting of the egt, ctx, 39k,orf51, gp37, iap2, odv-e56, p10 and p94 loci of the baculovirus genome.This recombinant baculovirus genome also preferably contains an AAVrecombinant genome in a locus selected from the polyhedrin, egt, ctx,39k, orf51, gp37, iap2, odv-e56, p10 and p94 loci of the baculovirusgenome, said AAV recombinant genome being inserted into a locusdifferent than the locus or loci used for the AAV rep and cap genes.

In one particular embodiment of the first variant, the recombinantbaculovirus genome according to the invention comprises at least oneexpression cassette for the AAV rep and/or cap genes in a locus selectedfrom the group consisting of the nonessential genes of the baculoviruswhich can be replaced with a sequence of interest without modifying thefunctioning of the baculovirus. Said at least one expression cassettefor the AAV rep and/or cap genes can in particular be included in alocus selected from the group consisting of the polyhedrin, ctx, egt,39k, orf51, gp37, iap2, p94, p10 and odv-e56 loci, in particular the egtlocus.

In another particular embodiment of the first variant, the recombinantbaculovirus genome according to the invention also comprises an AAVrecombinant genome. The locus for insertion of the AAV recombinantgenome is in particular selected from the group consisting of thepolyhedrin, egt, ctx, 39k, orf51, gp37, iap2, p94, p10 and odv-e56 loci.According to one particular embodiment, the locus selected for the AAVrecombinant genome is a locus different from the locus or loci selectedfor the expression cassette(s) for rep and/or cap. According to onepreferred embodiment, the AVV recombinant genome is inserted into thepolyhedrin locus (in particular at the level of the Tn7 recombinationsite).

According to a first preferred embodiment, the recombinant baculovirusgenome according to the invention comprises:

-   -   an AAV recombinant genome in the polyhedrin locus, and    -   an expression cassette for the AAV rep/cap genes, in a locus        selected from the group consisting of the ctx, egt, 39k, orf51,        gp37, iap2, p94, p10 and odv-e56 loci, in particular the egt        locus.

According to a second preferred embodiment, the recombinant baculovirusgenome according to the invention comprises:

-   -   an AAV recombinant genome in the p94 locus,    -   an expression cassette for the AAV rep/cap genes in a locus        selected from the group consisting of the polyhedrin, ctx, egt,        39k, orf51, gp37, iap2, p10 and odv-e56 loci, in particular the        egt locus.

The expression cassettes for the rep and cap genes are in particularselected according to the gene of interest to express from therecombinant AAV produced and to the type of cells to be transduced withsaid AAV. Those skilled in the art are able to select and produce theappropriate expression cassettes on the basis of their generalknowledge. By way of particular promoters, mention may be made of theearly/late baculovirus promoters, such as gp64, or very late baculoviruspromoters such as the polyhedrin (P_(Ph)) and p10 (P_(p10)) genepromoters, if the baculovirus is intended to infect insect cells. Theimmediate early promoters, such as IE1 (Immediate Early 1), can also beused in the context of the invention, with the possibility offunctioning in mammalian cells for example. By way of polyadenylationsequences, mention may in particular be made of the tryptophanhydroxylase (Tph) polyadenylation sequences, or polyadenylationsequences of baculovirus genes.

The rep and cap genes can be selected according to the type ofrecombinant AAV that it is desired to produce. They can be selected fromthe rep and cap genes of AAV of any serotype. The rep and cap genes canbe included in different expression cassettes or in a single cassette.According to one preferred embodiment, a single expression cassette isused for the expression of the rep and cap genes, According to oneembodiment variant, the expression cassette for the AAV rep/cap genescomprises said genes in reverse orientation. These genes in reverseorientation can in particular each be under the control of differentpromoters, especially different baculovirus promoters, in particulardifferent very late promoters. For example, the very late promoters inquestion can in particular correspond to the P_(P10) and P_(Ph)baculovirus promoters. According to one particularly preferredembodiment, the expression cassette for rep and cap is produced andinserted into the recombinant baculovirus genome of the inventionaccording to the procedures described in Smith et al., 2009; Mol. Ther.17: 1888-1896. According to one particular mode, the expression cassettecorresponds to that described in the examples below, allowing theexpression of the rep2 and cap8 gene products, and therefore theproduction of recombinant AAV vectors of rAAV8 type, comprising AAV8capsid proteins, and therefore having the tropism of this particularserotype. This expression cassette is preferentially introduced into thebaculovirus genome by transposition, according to procedures well knownin the field, in particular using the Bac-to-Bac system sold by thecompany Invitrogen.

According to one particular embodiment, the expression cassette for theAAV rep/cap genes is inserted into the egt locus, in particularaccording to the method described in the examples.

The AAV recombinant genome comprises a 5′ ITR (for Inverted TerminalRepeat), at least one heterologous nucleotide sequence of interest underthe control of a promoter which is effective in the target cell of therecombinant AAV produced, and a 3′ ITR. The ITRs can be derived from anyAAV serotype known to those skilled in the art.

The term “heterologous nucleotide sequence of interest” is intended tomean a nucleotide sequence which is not a baculovirus gene or an AAVgene and which, when it is expressed in a cell of interest (also termed“target cell”), makes it possible to obtain a desired effect. Theheterologous nucleotide sequence may in particular encode a protein, aninterfering RNA, an antisense RNA, a microRNA or snRNA. The desiredeffect can in particular correspond to the expression of theheterologous nucleotide sequence in cells or tissues of a patient. Thus,the heterologous nucleotide sequence can in particular be administeredin order to obtain a therapeutic effect. In this respect, therecombinant AAV produced will be usable as a gene therapy vector. Theheterologous nucleotide sequence may thus allow the production of atherapeutic protein, for example a protein which is deficient in adiseases, or an interfering RNA in cells requiring reduction of theexpression of an abnormal protein, or an snRNA (small nuclear RNA)involved in the removal of a mutated exon responsible for thenonfunctionality of a protein.

The target cell corresponds to any cell in which the expression of theheterologous nucleotide sequence may be of interest, in particulartherapeutic interest. The promoter present in the AAV genome will thusbe a promoter which allows the expression of the heterologous nucleotidesequence in the target cell. This promoter may be constitutive,inducible or specific for a particular cell or tissue.

Of course, those skilled in the art are familiar with the concepts ofgene therapy and will adapt the constituent elements of the presentinvention to the needs thereof.

The recombinant baculovirus genome can also comprise any AAV sequencewhich makes it possible to improve the amount or the quality of therecombinant AAV. In this respect, mention may be made of the insertion,into one of the loci mentioned above, of the gene encoding the AAPprotein (or Assembly Activating Protein—Sonntag et al., Proc Natl AcadSci USA. 2010 Jun. 1; 107(22):10220-5).

According to a second variant of the invention, the recombinantbaculovirus genome described is a baculovirus genome for the productionof a lentiviral vector.

In this respect, the invention also relates to a recombinant baculovirusgenome comprising one or more expression cassettes for the gag/pol andrev genes from lentivirus (for example originating from HIV-1) and/orenv gene chosen according to the desired tropism, but preferably the Gprotein originating from the vesicular stomatitis virus (VSV-G), saidone or more expression cassettes being inserted into a locus selectedfrom the group consisting of the egt, ctx, 39k, orf51, gp37, iap2,odv-e56, p10 and p94 loci of the baculovirus genome. This recombinantbaculovirus genome also preferably contains a lentivirus recombinantgenome in a locus selected from the polyhedrin, egt, ctx, 39k, orf51,gp37, iap2, odv-e56, p10 and p94 loci of the baculovirus genome, saidlentivirus recombinant genome being inserted into a locus different fromthe locus or loci used for the lentivirus gag/pol and rev genes and alsothe env gene.

In one particular embodiment of the first variant, the recombinantbaculovirus genome according to the invention comprises at least oneexpression cassette for the lentivirus gag/pol and rev genes and alsothe env gene, in a locus selected from the group consisting of thenonessential genes of the baculovirus which can be replaced with asequence of interest without modifying the functioning of thebaculovirus. Said at least one expression cassette for the lentivirusgag/pol and rev genes and also the env gene can in particular beincluded in a locus selected from the group consisting of thepolyhedrin, ctx, egt, 39k, orf51, gp37, iap2, p94, p10 and odv-e56 loci.

In another particular embodiment of the first variant, the recombinantbaculovirus genome according to the invention also comprises alentivirus recombinant genome. The locus for insertion of the lentivirusrecombinant genome is in particular selected from the group consistingof the polyhedrin, egt, ctx, 39k, orf51, gp37, iap2, p94, p10 andodv-e56 loci. According to one particular embodiment, the locus chosenfor the lentivirus recombinant genome is a locus different than thelocus or loci chosen for the expression cassette(s) for gag/pol, revand/or env. According to one preferred embodiment, the lentivirusrecombinant genome is inserted into the polyhedrin locus (in particularat the level of the Tn7 recombination site).

According to a first preferred embodiment, the recombinant baculovirusgenome according to the invention comprises:

-   -   a lentivirus recombinant genome in the polyhedrin locus, and    -   an expression cassette for the lentivirus gag/pol and rev genes        and also the env gene in a locus selected from the group        consisting of the ctx, egt, 39k, orf51, gp37, iap2, p94, p10 and        odv-e56 loci.

According to a second preferred embodiment, the recombinant baculovirusgenome according to the invention comprises:

-   -   a lentivirus recombinant genome in the p94 locus,    -   an expression cassette for the lentivirus gag/pol and rev genes        and also the env geme in a locus selected from the group        consisting of the polyhedrin, ctx, egt, 39k, orf51, gp37, iap2,        p10 and odv-e56 loci.

The expression cassettes for the lentivirus gag/pol and rev genes andalso the env gene are in particular selected according to the gene ofinterest to be expressed from the recombinant lentivirus produced and tothe type of cells to be tranduced with said lentivirus. Those skilled inthe art are able to select and produce the appropriate expressioncassettes on the basis of their general knowledge. By way of particularpromoters, mention may be made of the early/late baculovirus promoters,such as gp64, or very late baculovirus promoters such as the polyhedrin(P_(Ph)) and p10 (P_(p10)) gene promoters, if the baculovirus isintended to infect insect cells. The immediate early promoters, such asIE1 (Immediate Early 1) are also usable in the context of the invention,with the possibility of functioning in mammalian cells for example. Byway of polyadenylation sequences, mention may in particular be made ofthe tryptophan hydroxylase (Tph) polyadenylation sequences, orpolyadenylation sequences of baculovirus genes.

The term “heterologous nucleotide sequence of interest” is intended tomean a nucleotide sequence which is not a baculovirus gene or alentivirus gene and which, when it is expressed in a cell of interest(also referred to as “target cell”) makes it possible to obtain adesired effect. The heterologous nucleotide sequence can in particularencode a protein, an interfering RNA, an antisense RNA, a microRNA or ansnRNA. The desired effect can in particular correspond to the expressionof the heterologous nucleotide sequence in cells or tissues of apatient. Thus, the heterologous nucleotide sequence can in particular beadministered in order to obtain a therapeutic effect. In this respect,the recombinant lentivirus produced will be usable as a gene therapyvector. The heterologous nucleotide sequence may thus allow theproduction of a therapeutic protein, for example a protein which isdeficient in a disease, or an interfering RNA in cells requiringreduction of the expression of an abnormal protein, or an snRNA (smallnuclear RNA) involved in the removal of a mutated exon responsible forthe nonfunctionality of a protein.

The target cell corresponds to any cell in which the expression of theheterologous nucleotide sequence may be of interest, in particulartherapeutic interest. The promoter present in the lentivirus genome willthus be a promoter which allows the expression of the heterologousnucleotide sequence in the target cell. This promoter may beconstitutive, inducible or specific for a particular cell or tissue.

Of course, those skilled in the art are familiar with the concepts ofgene therapy and will adapt the constituent elements of the presentinvention to the needs thereof.

The recombinant baculovirus genome may be derived from any baculoviruscomprising the polyhedrin locus (or equivalent), and at least one ormore of the other loci mentioned above (or one or more equivalent loci).

According to one particular embodiment, the recombinant baculovirusgenome according to the invention is a bacmid. In the context of thepresent invention, a “bacmid” is a baculovirus genome comprising geneticelements for maintaining and amplifying a baculovirus genome in aprokaryotic cell. It may in particular comprise a bacterial origin ofreplication, a selectable gene, in particular a gene for resistance toan antibiotic such as kanamycin, and a recombination cloning site suchas “Tn7”, which are inserted into a baculovirus locus, such as thepolyhedrin locus. According to one variant, the recombinant bacmidaccording to the invention comprises an origin of replication, akanamycin resistance gene and a Tn7 recombination cloning site in thepolyhedrin locus (in particular the AcMNPV bacmid described in Luckow etal., 1993; J. Virol. 67:4566-4579). Thus, the recombinant baculovirusgenome can correspond to a sequence capable of replicating in insectcells and in a prokaryotic organism such as E. coli. In particular, anybaculovirus genome comprising a DNA construct which allows the genome tobe maintained in a prokaryotic organism, in particular a BAC replicon,can be used. According to one preferred aspect, the baculovirus genomeof the invention is derived from an AcMNPV or SpliNPV backbone. Theposition of the ctx, egt, 39k, orf51, gp37, iap2 and odv-e56 geneticloci in the AcMNPV reference sequence (accession number NC001623) are inparticular described in Table 1 of international application WO2010/055292. With regard to the p94 and p10 genetic loci, their positionis shown in FIG. 1 (AcMNPV reference sequence—accession numberNC001623).

According to one particular embodiment, the recombinant baculovirusgenome is derived from AcMNPV and comprises a deletion of the chitinase,cathepsin and p10 genes. Thus, according to this embodiment, theinvention relates to a recombinant AcMNPV baculovirus genome devoid ofthe chitinase, cathepsin and p10 genes and comprising an expressioncassette for the AAV rep/cap genes in a locus selected from the groupconsisting of the egt, polyhedrin, ctx, 39k, orf51, gp37, iap2 andodv-e56, p10 and p94 loci, in particular the egt locus.

In one variant of this embodiment, the bacmid comprises, moreover, anAAV recombinant genome in the polyhedrin locus (Tn7 of the bacmid).

In another variant of this embodiment, the baculovirus genome comprises,moreover, an AAV recombinant genome in the p94 locus.

The deletion of the chitinase, cathepsin and p10 genes in thebaculovirus backbone allows a highly efficient production of AAVvectors, enabling reduced proteolytic degradation, in particular of theVP1 and VP2 proteins, and thus an increase in the infectivity and theeffectiveness in vivo. The deletion of these genes can be carried outaccording to any procedure known to those skilled in the art. Use willmore particularly be made of the method described in the examplesimplementing the homologous recombination process (Datsenko and Wanner,2000; Proc Natl Acad Sci USA. 97(12):6640-6645) in E. coli bacteriacontaining the bacmid to be modified (in particular the AcMNPV bacmiddescribed in Luckow et al., 1993; J. Virol. 67:4566-4579).

According to one particular embodiment, the chi/v-cath genes(nucleotides 105282-107954 according to the genetic map of AcMNPV (Ayreset al., 1994)) and p10 (nucleotides 118839-119121) gene are deleted.

According to one variant of the embodiment comprising a deletion of thechitinase, cathepsin and p10 genes, the deletion of the p10 gene is notaccompanied by a deletion of the promoter of the p10 gene. In otherwords, the recombinant baculovirus genome deficient for the chitinase,cathepsin and p10 genes comprises a functional P_(P10) promoter(corresponding to the nucleotides 118739-118836 of the genetic map ofAcMNPV).

According to another variant of the embodiment comprising a deletion ofthe chitinase, cathepsin and p10 genes, the deletion of the p10 gene isaccompanied by a deletion of the adjacent p26 and p74 genes. Accordingto one particular aspect of this embodiment, the deletion of the p26,p10 and p74 genes corresponds to nucleotides 118044-121072 of thegenetic map of AcMNPV (Ayres et al., 1994).

According to a second aspect, the invention relates to a recombinantbaculovirus comprising a genome corresponding to the baculovirus genomedescribed above. According to one preferred embodiment, the recombinantbaculovirus comprises a genome corresponding to the recombinant bacmiddescribed above.

According to a third aspect, the invention relates to a method forproducing a baculovirus according to the invention, comprising culturinga prokaryotic cell containing the recombinant bacmid defined above underconditions suitable for the production of a baculovirus. Theseconditions are well known to those skilled in the art (Smith et al.,2009, above; Luckow et al., 1993, above).

According to a fourth aspect, the invention relates to a eukaryotic orprokaryotic cell containing the baculovirus genome defined above. Thecell may in particular be a mammalian or insect eukaryotic cell, inparticular an insect cell which has been infected with a recombinantbaculovirus as defined above.

Among the insect cells, preference will be given to those derived fromthe Spodoptera frugiperda or Trichoplusia ni lines, for example theSf21, Sf9, High Five or TN 5B1-4 cells. Among the mammalian cells,mention may in particular be made of the HEK293 line, which is known tobe capable of being infected with a baculovirus. In the latter case, thepromoter(s) present in the expression cassette for the rep and cap geneswill be suitable for expression in mammalian cells. Mention may inparticular be made of the CMV promoter and other promoters well known inthe field.

According to a fifth aspect, the invention relates, moreover, to amethod for producing a viral vector, in particular a viral gene therapyvector, comprising culturing the recombinant baculovirus as definedabove with a cell, in particular an insect cell or a mammalian cell,under conditions which allow the infection of the cell with thebaculovirus and the production of said viral vector.

With regard to the production of enveloped vectors (such as retroviralvectors), this involves a mammalian cell (for example an HEK293 cell).

According to one particular embodiment, the method according to theinvention is a method for producing a recombinant AAV comprisingculturing the recombinant baculovirus defined above with a cell, inparticular an insect cell (e.g. an Sf21, Sf9, High Five or TN 5B1-4cell), capable of being infected with said baculovirus, under conditionswhich allow the infection of the cell with the baculovirus and theproduction of said recombinant AAV. Thus, it is possible to produce arecombinant AAV from an infection with a single baculovirus. Particular,nonlimiting, conditions for producing a recombinant AAV according to theinvention are in particular described in the examples. Of course, thoseskilled in the art are able to adapt these production conditions on thebasis of their general knowledge (Smith et al., above).

By virtue of this method, a recombinant AAV production is obtained whichis at least 5 times greater than that obtained with a system requiringinfection with two baculoviruses, such as the system described by Smithet al.

According to another particular embodiment, the method according to theinvention is a method for producing a recombinant lentivirus, comprisingculturing the recombinant baculovirus as defined above with a mammaliancell (for example an HEK293 cell) capable of being infected with saidbaculovirus, under conditions which allow the infection of the cell withthe baculovirus and the production of said recombinant lentivirus.

The examples below are provided in order to illustrate the invention.

Examples Materials and Methods Sequences

TABLE 1 primer sequences Primer Sequence 5′ to 3′ Use* EGT-lox-FTTACGGTCGTCAAGCCCAAACTGTTTGCGTATTCAACTAAAACTTATTGCGinsertion of rep2/cap8GTAATATCACTACCGTTCGTATAGCATACATTATACGAAGTTATAATAGGinto the AcMNPV bacmid AACTTCATTTAAATGGCGC (SEQ ID No. 1)at the level of the EGT locus (11634-12486) EGT-SV40-RTCCCGGCTTCCAAGGCCTCGTCGCTCGATTGTAGTCCGCCTTGCGTAATAAinsertion of rep2/cap8 ACGCCGCCATTTTTTTATGACGCAGCACGGinto the AcMNPV bacmid CAGACATGATAAGATACATTGATGAGTTTG (SEQ ID No. 2)at the level of the EGT locus (11634-12486) EGT-ATGACTATTCTCTGCTGGC (SEQ ID No. 3) verification Control 150F EGT-ATTGGCCGTGTTTCCTAC (SEQ ID No. 4) verification Control 150R M13 PUC FCCAGTCACGACGTTGTAAAACG (SEQ ID No. 5) verification of the bacmidstransposed M13 PUC R AGCGGATAACAATTTCACACAGG (SEQ ID No. 6)verification of the bacmids transposed GentaAGCCACCTACTCCCAACATC (SEQ ID No. 7) verification of the bacmidstransposed CC-KO-F CCGCTGTTGAAACAATATTTTATAATACCCTGTTTATAGTTAACAATGTCGinactivation of the GCAGCGTCTATGGCCATAGGAATAGGGCCTACCGTTCGTATAATGTATGCchitinase/cathepsin genes TATACGAAGTTAT (SEQ ID No. 8) nt 105771-107700CC-KO-R CCGCTGTTGAAACAATATTTTATAATACCCTGTTTATAGTTAACAATGTCGinactivation of the GCAGCGTCTATGGCCATAGGAATAGGGCCTACCGTTCGTATAATGTATGCchitinase/cathepsin genes TATACGAAGTTAT (SEQ ID No. 9) nt 105771-107700chitinase- CGCGGCCGTACATGGCGACGCCCA (SEQ ID No. 10) verification 105625Fcathepsin- GTTTTTAAAGGTCCAATATGGAATG (SEQ ID No. 11) verification107849R p10-KO-F TTGTATATTAATTAAAATACTATACTGTAAATTACATTTTATITACAATCTinactivation of the p10ACCGTTCGTATAGCATACATTATACGAAGTTAT (SEQ ID No. 12)encoding sequence (from the start codon to the stopcodon) nt 118839-119121 P10-KO-RGAATCGTACGAATATTATAAAACAATTGATTTGTTATTTTAAAAACGATTTinactivation of the p10ACCGTTCGTATAATGTATGCTATACGAAGTTAT (SEQ ID No. 13)encoding sequence (from the start codon to the stopcodon) nt 118839-119121 p10-118725-FCCGGGACCTTTAATTCAACCCAACA (SEQ ID No. 14) verification p10-119259-RCAGCATTTGTTATACACACAGAACT (SEQ ID No. 15) verification *numberingaccording to Ayres et al., Virology. 1994 Aug. 1; 202(2):586-605.

Baculovirus Gene Deletion

The deletion of cathepsin and of chitinase in the wild-type AcMNPVbacmid was carried out using the E. coli DH10Bac strain containing theAcMNPV bacmid (Luckow et al., 1993, cf above) and transformed with pKD46(Datsenko and Wanner, 2000, PNAS Vol 97 (12) pages 6640-6645). A PCRproduct necessary for the inactivation of the cathepsin/chitinase geneswas generated by means of the CC-KO-F and CC-KO-R primers (table 1). Theinactivation of the genes was carried out according to the methoddescribed by Marek et al., 2011 and evaluated using thechitinase-105625F and cathepsin-107849R primers (table 1). Thesuppression of the CAT marker gene of the cathepsin/chitinase nullbacmid (AcbacΔCCΔcat) was carried out according to the method describedby Marek et al. (Marek et al., 2011, Biotechnol Bioeng, Vol 108 (5)pages 1056-67) and verified by PCR and sequencing, using the primersmentioned above. The inactivation of the p10 coding sequence inAcbacΔCCΔcat was carried out in the same way, with a PCR product beinggenerated with the p10-KO-F/p10-KO-R primers (table 1). The verificationof the correct inactivation of the gene was carried out by PCR andsequencing with the pair of primers p10-118725-F/p10-119259-R (table 1).The final gene inactivation allows the production of thecathepsin/chitinase/p10 null bacmid (AcbacΔCCΔp10).

Insertion of the Rep2/Cap8 Cassette at the egt Locus of the AcMNPVBacmid

The insertion of the expression cassette for the AAV rep2 and cap8 genesat the egt locus was carried out in the genome of the bacmid, alreadyinactivated for the chitinase, cathepsin and p10 genes.

The rep2/cap8 expression cassette was amplified by PCR from the pSR660plasmid, by virtue of the EGT-lox-F and EGT-SV40-R primers. Theinsertion of this PCR product into the genome of the bacmid was carriedout according to the method described by Marek et al., 2011. Briefly,the rep2/cap8 expression cassette was coupled to a gene for resistanceto the antibiotic chloramphenicol, bordered by the lox66 and lox71sequences (Suzuki et al., 2005; appl Environ Microbiol. 71(12)8472-8480). These two genetic elements make it possible to subsequentlyremove this resistance gene, by the action of the Cre recombinase, whichcan then be used for successive series of deletions or insertions ofgenes in the genome of the bacmid. The cassette described above is thenamplified by PCR by virtue of the EGT-lox-F and EGT-SV40-R primers. ThisPCR product is purified on agarose gel and treated with the DpnIrestriction enzyme. It is then used to chemically transform competentbacteria containing the bacmid, already inactivated for the chitinase,cathepsin and p10 genes, the pKD46 plasmid (Datsenko and Wanner 2000).The expression of the lambda phase Red operon genes encoded by the pKD46plasmid is induced by adding L-arabinose at 0.1% (weight/volume). Thechloramphenicol-resistant recombinant bacteria are analyzed by PCR inorder to verify the insertion of the rep2/cap8 expression cassette intothe genome of the bacmid already inactivated for the chitinase,cathepsin and p10 genes, at the egt locus, using the EGT-Control 150Fand EGT-Control 150R primers (table 1). This insertion made it possibleto obtain the Monobac-AcbacΔCCΔp10-rep2cap8(EGT) bacmid.

Insertion of the rep2/cap8 Cassette and of the Recombinant Genome ofrAAV into the Bacmid at the Tn7 Site

E. coli DH10b bacteria containing either the AcbacΔCCΔp10 bacmid or theMonobac-AcbacΔCCΔp10-rep2cap8(EGT) bacmid were transformed with thepMON7124 plasmid (Luckow et al., 1993). Either the AAV recombinantgenome encoding the murine secreted alkaline phosphatase (mSeAP)reporter gene under the control of the CMV promoter and surrounded bythe AAV ITRs, or the expression cassette for the AAV rep2 and cap8genes, was inserted by recombination (Luckow et al., 1993) into thesebacteria, and also into DH10bac bacteria containing the wild-type Acbacbacmid (Luckow et al. 1993). These recombinations were respectivelycarried out using the pFBD-mSeAP and pFBD-SR660 plasmids. Theserecombinations made it possible to generate the bacmids:

-   -   AcbacWT-rep2/cap8(Tn7); AcbacΔCCΔp10-rep2/cap8(Tn7) allowing the        expression of the rep2 and cap8 genes from the Tn7 site.    -   AcbacWT-mSeAP(Tn7); AcbacΔCCΔp10-mSeAP(Tn7) containing the rAAV        genome encoding the mSeAP gene, at the Tn7 site of the bacmid.    -   AcbacΔCCΔp10-rep2/cap8(EGT)mSeAP(Tn7) allowing the expression of        the rep2 and cap8 genes from the egt locus and containing the        rAAV genome encoding the mSeAP gene at the Tn7 site of the        bacmid.    -   Finally, the AcbacΔCCΔp10-rep2/cap8(EGT) bacmid allows the        expression of the rep2 and cap8 genes from the egt locus, but        has not received the recombinant genome of rAAV-mSeAP at the Tn7        site.        Cell Line, Baculovirus and rAAV Production

The Sf9 cells are maintained at 27° C. in SF900II medium (Invitrogen) inone-liter Bellco spinners. The baculoviruses are generated according tothe Bac-to-Bac protocol from Invitrogen, and then amplified in Sf9 cellsuspension cultures, in 100 ml Bellco spinners. To produce the rAAVvectors, the Sf9 cells are infected with one or two baculovirus(es)encoding the AAV rep2 and cap8 genes and containing the mSeAP cassetteof the rAAV genome. 70 ml of Sf9 cells at a density of 10⁶cell/ml arethus infected with an MOI of 0.1 in order to produce the rAAV vectors.96 hours after the production, an aliquot is removed in order to carryout titrations of the rAAV vectors, the rest is stored at −80° C.

rAAV Vector Purification and Characterization

The rAAV vectors are purified from the whole cell culture on an AVBsepharose immunoaffinity column (GE Healthcare) according to therecommendations of Smith et al., 2009. The purified rAAV vectors areanalyzed (5×10⁺¹⁰ vg) on an “SDS-PAGE” polyacrylamide gel (NuPAGesystem, Invitrogen). After migration, the gel is stained with coomassieblue.

Determination of the rAAV Vector Viral Genome Titers

In order to determine the titer in terms of viral genomes (vg) of therAAV vectors produced, a viral DNA extraction is carried out directlyfrom the whole of the cell culture, or else from purified rAAV vectorsamples. This extraction is carried out using the MagNA Pure DNA andviral NA small volume kit system (MagNA Pure 96, Roche). A real-timequantitative PCR is then carried out, with primers which hybridize theITRs of the AAV. The absolute quantification is carried out relative toa reference plasmid which contains the regions amplified by quantitativePCR and the number of copies of which is known. The titrations arecarried out at the same time, on the same plate and under the sameconditions and by an independent operator, in order to reduce theexperimental variability as much as possible.

Protein Detection by Western Blot

The samples of culture containing the rAAV vector or purified samplesare analyzed by Western blot in order to detect the presence of the VPproteins and of the Rep proteins of AAV. The proteins are visualizedaccording to the method developed by LI-COR, with an Odyssey apparatusand the Odyssey 2.1 software. The primary antibodies used are mouseanti-VP IgG1 clone B1 (Progen) for detection of the VP proteins andmouse anti-Rep IgG1 clone 303.9 (Progen) for detection of the Repproteins. These antibodies are used respectively at a 1/250^(th) and1/100^(th) dilution in infrared imaging system blocking buffer, LI-COR.The goat secondary antibodies used are directed against the primaryantibodies and coupled to the “Dye 680” fluorochrome from LI-COR. TheP35 baculovirus protein is also detected using a specific primaryantibody and a secondary antibody coupled to “Dye 800” from LI-COR.

Statistical Analysis

The statistical significance of the differences observed for the titersof rAAV obtained during the production was analyzed. A Fisher test wascarried out in order to determine the equality of two variances. AStudent's test was subsequently performed. The Excel software was usedfor these analyses.

Results

Generation of a Baculovirus Expressing, at the egt Locus, the AAV rep2and cap8 Genes

An already modified bacmid genome was used to insert the AAV rep2 andcap8 genes into the genome of the AcMNPV bacmid. We previously showedthat the use of a bacmid inactivated for the chitinase, cathepsin andp10 genes reduced the proteolysis of the rAAV capsid for certainserotypes. The insertion of the AAV rep2 and cap8 genes at the egt locuswas thus carried out in the AcbacΔCCΔp10 bacmid, according to themethodology developed by Marek et al., 2011 (FIG. 1). This insertion wasverified by PCR and sequencing. It resulted in the creation of theAcbacΔCCΔp10-rep2cap8(EGT) bacmid. This bacmid still has theconventional recombination cloning site, Tn7 (Luckow et al., 1993), intowhich the rAAV genome expressing the mSeAP gene could be inserted, thusgenerating the AcbacΔCCΔp10-rep2cap8(EGT)SeAP(Tn7) construct.

In parallel, the control bacmids were generated with the insertion atthe Tn7 site of the rAAV genome or of the expression cassette for theAAV rep2 and cap8 genes. These control bacmids were generated on anunmodified genetic background or on the genetic background inactivatedfor the chitinase, cathepsin and p10 genes.

After recombination, the bacmid DNAs were extracted and purifiedaccording to the Bac-to-Bac protocol (Invitrogen) and the absence ofnonrecombinant bacmid was verified by PCR. The bacmids were transfectedinto Sf9 cells, plate-purified by lysis plaque and amplified. Nodifference in terms of baculovirus titer (pfu/ml) was observed betweenall the constructs.

Insertion of the AAV rep2 and cap8 Genes at the Egt Locus AllowsExpression of Said Genes

First of all, the capacity to generate the AcbacΔCCΔp10-rep2cap8(EGT)baculovirus in Sf9 cells, without modifying the viral titer, confirmsthe possibility of inserting a gene expression cassette at the egt locuswithout modifying the viability of the baculovirus, as previouslyobserved by Noad et al., 2009.

The protein expression level can be modified according to the site ofinsertion of the gene into the baculovirus genome (Noad et al., 2009).The egt locus was thus chosen for inserting the rep2/cap8 expressioncassette on the basis of an equivalence of expression in comparison withthe expression directed from the Tn7 site (Noad and al.).

As observed in FIG. 2, the AAV Rep and VP proteins are expressed atcomparable levels, whether the expression cassette is inserted at theegt locus as in the AcbacΔCCΔp10-rep2cap8(EGT) construct (FIG. 2, MB C1and C2) or at the Tn7 site for the AcbacΔCCΔp10 and AcbacWT constructs(FIG. 2, ΔCCP-SR660 C1 and C2; WT-SR660 C1 and C2).

After insertion of the rAAV mSeAP genome at the Tn7 site of the bacmid(AcbacΔCCΔp10-rep2cap8(EGT)SeAP(Tn7)), the expression of the rep2 andcap8 genes remains equivalent to that observed for this same baculovirusnot containing the rAAV genome (FIG. 3).

rAAV Production by a Single Baculovirus Improves Cell Productivity

rAAV productions were carried out in spinners under identicalconditions. The rAAV titers were then determined and are indicated inFIG. 4. Conventional production with 2 baculoviruses (Smith et al.,2009) using the AcbacWT-rep2/cap8(Tn7) and AcbacWT-mSeAP(Tn7)baculoviruses makes it possible to obtain a titer of 1.44×10¹⁰ vg/ml ofrAAV. The equivalent production using this time the baculovirusesinactivated for the chitinase, cathepsin and p10 genes,AcbacΔCCΔp10-rep2/cap8(Tn7) and AcbacΔCCΔp10-mSeAP(Tn7) makes itpossible to obtain titers of 2.23×10¹⁰ vg/ml. These results are in thesame order of magnitude as those obtained for productions carried outwith the unmodified bacmid genome. In order to verify the locus effectof moving the rep2/cap8 expression cassette from the Tn7 site to the egtlocus, productions were carried out with the AcbacΔCCΔp10-rep2/cap8(EGT)baculovirus and the AcbacΔCCΔp10-mSeAP(Tn7) baculovirus. The titerobtained is 4.63×10¹⁰ vg/ml of rAAV, i.e. double the titer obtained incomparison with the productions where the rep2/cap8 cassette is insertedat the Tn7 site (p=0.005). This result shows a positive locus effect forthe production of rAAV when the rep2/cap8 expression cassette isinserted at the egt locus instead of the Tn7 site. Finally, rAAVproduction using a single baculovirus,AcbacΔCCΔp10-rep2/cap8(EGT)-mSeAP(Tn7), resulted in 9.4×10¹⁰ vg/ml, thusenabling an increase by a factor 6.5 (p=0.006) in productivity comparedwith the rAAV production carried out with two baculovirusesAcbacWT-rep2/cap8(Tn7) and AcbacWT-mSeAP(Tn7). After purification of thevectors produced, a 4-fold gain is still found in favor of the rAAVproduction carried out with a single baculovirus,AcbacΔCCΔp10-rep2/cap8(EGT)-mSeAP(Tn7), in comparison with the rAAVproduction carried out with two baculoviruses AcbacWT-rep2/cap8(Tn7) andAcbacWT-mSeAP(Tn7) (FIG. 6).

Moreover, the analysis of the protein profile of the recombinant AAVvectors purified shows a disappearance of recombinant AAV capsiddegradation bands associated with the activity of the baculoviruscathepsin (FIG. 6). These bands are visible for the AAV vectors producedwith the wild-type baculovirus (FIG. 6, lane 1). These degradation bandsare no longer present in the recombinant AAV vectors produced with thebaculoviruses for which the chitinase, cathepsin and p10 genes areremoved from the baculovirus genome (FIG. 6, lanes 2; 3; 4). Thisreduction in the degradation of the recombinant AAV vectors isassociated with an increase in in vivo infectivity for these vectors.

1. A recombinant baculovirus genome comprising one or more expressioncassettes for the protein components required for the production of aheterologous viral vector, and a recombinant genome of a heterologousviral vector, said expression cassettes and said recombinant genome of aheterologous viral vector being inserted into one or more locus selectedfrom the group consisting of the egt, polyhedrin, ctx, 39k, orf51, gp37,iap2 and odv-e56, p10 and p94 loci.
 2. The baculovirus genome as claimedin claim 1, comprising at least one expression cassette for the AAV repand/or cap genes, inserted into said one or more loci.
 3. Therecombinant baculovirus genome as claimed in claim 2, said rep and capgenes being contained in a single expression cassette, said cassettebeing more particularly inserted into the egt locus.
 4. The recombinantbaculovirus genome as claimed in claim 2, the recombinant genome of aheterologous viral vector being an AAV recombinant genome inserted intoa locus different than the locus or loci used for the AAV rep and capgenes, said recombinant genome of a heterologous viral vector being inparticular inserted at the level of the polyhedrin locus.
 5. Arecombinant baculovirus genome comprising one or more expressioncassettes for the AAV rep and/or cap genes, said one or more expressioncassettes being inserted into a locus selected from the group consistingof the egt, ctx, 39k, orf51, gp37, iap2, odv-e56, p10 and p94 loci ofthe baculovirus genome.
 6. The recombinant baculovirus genome as claimedin claim 5, said rep and cap genes being contained in a singleexpression cassette, said cassette being more particularly inserted intothe egt locus.
 7. The recombinant baculovirus genome as claimed in claim5, also comprising an AAV recombinant genome in a locus selected fromthe polyhedrin, egt, ctx, 39k, orf51, gp37, iap2, odv-e56, p10 and p94loci of the baculovirus genome, said AAV recombinant genome beinginserted into a locus different than the locus or loci used for the AAVrep and cap genes.
 8. The recombinant baculovirus genome as claimed inclaim 1 or 5, said baculovirus genome being derived from AcMNPV.
 9. Therecombinant baculovirus genome as claimed in claim 1 or 5, in which thechitinase, cathepsin and p10 genes are deleted.
 10. The recombinantbaculovirus genome as claimed in claim 4 or 7, wherein the AAVrecombinant genome comprises a heterologous gene encoding a protein, aninterfering RNA or an antisense RNA, which is in particular therapeutic.11. The recombinant baculovirus genome as claimed in claim 1 or 5, saidrecombinant baculovirus genome being a bacmid.
 12. A recombinantbaculovirus containing a recombinant baculovirus genome as claimed inclaim 1 or 5, as genome.
 13. A method for producing a recombinantbaculovirus, comprising culturing a prokaryotic cell containing therecombinant bacmid defined in claim 11 under conditions suitable for theproduction of a baculovirus.
 14. A eukaryotic or prokaryotic cellcontaining the recombinant baculovirus genome as claimed in claim 1 or5, or infected with the recombinant baculovirus of claim
 12. 15. Thecell as claimed in claim 14, said cell being an insect cell derived fromthe Spodoptera frugiperda or Trichoplusia ni lines, for example theSf21, Sf9, TN 5B1-4 or High Five cells.
 16. A method for producing arecombinant virus, in particular a recombinant AAV, comprising culturingone or more recombinant baculoviruses as claimed in claim 12, with acell, in particular an insect cell (for example an Sf9, Sf21, TN 5B1-4or High Five cell), capable of being infected with said baculovirus,under conditions which allow the infection of the cell with thebaculovirus and the production of said recombinant virus.
 17. The methodas claimed in claim 16, comprising culturing a single baculoviruscomprising in its genome all of the elements required for the productionof said recombinant virus.